/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You under the Apache License, Version 2.0
 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */
package org.apache.tomcat.websocket.server;

import org.apache.coyote.http11.upgrade.AbstractServletInputStream;
import org.apache.coyote.http11.upgrade.AbstractServletOutputStream;
import org.apache.coyote.http11.upgrade.servlet31.HttpUpgradeHandler;
import org.apache.coyote.http11.upgrade.servlet31.ReadListener;
import org.apache.coyote.http11.upgrade.servlet31.WebConnection;
import org.apache.coyote.http11.upgrade.servlet31.WriteListener;
import org.apache.juli.logging.Log;
import org.apache.juli.logging.LogFactory;
import org.apache.tomcat.util.res.StringManager;
import org.apache.tomcat.websocket.Transformation;
import org.apache.tomcat.websocket.WsIOException;
import org.apache.tomcat.websocket.WsSession;

import javax.servlet.http.HttpSession;
import javax.websocket.*;
import javax.websocket.CloseReason.CloseCodes;
import java.io.IOException;
import java.util.List;
import java.util.Map;

/**
 * Servlet 3.1 HTTP upgrade handler for WebSocket connections.
 */
public class WsHttpUpgradeHandler implements HttpUpgradeHandler {

	private static final Log log =
			LogFactory.getLog(WsHttpUpgradeHandler.class);
	private static final StringManager sm =
			StringManager.getManager(Constants.PACKAGE_NAME);

	private final ClassLoader applicationClassLoader;

	private Endpoint ep;
	private EndpointConfig endpointConfig;
	private WsServerContainer webSocketContainer;
	private WsHandshakeRequest handshakeRequest;
	private List<Extension> negotiatedExtensions;
	private String subProtocol;
	private Transformation transformation;
	private Map<String, String> pathParameters;
	private boolean secure;
	private WebConnection connection;

	private WsSession wsSession;

	public WsHttpUpgradeHandler() {
		applicationClassLoader = Thread.currentThread().getContextClassLoader();
	}

	public void preInit(Endpoint ep, EndpointConfig endpointConfig,
	                    WsServerContainer wsc, WsHandshakeRequest handshakeRequest,
	                    List<Extension> negotiatedExtensionsPhase2, String subProtocol,
	                    Transformation transformation, Map<String, String> pathParameters,
	                    boolean secure) {
		this.ep = ep;
		this.endpointConfig = endpointConfig;
		this.webSocketContainer = wsc;
		this.handshakeRequest = handshakeRequest;
		this.negotiatedExtensions = negotiatedExtensionsPhase2;
		this.subProtocol = subProtocol;
		this.transformation = transformation;
		this.pathParameters = pathParameters;
		this.secure = secure;
	}

	@Override
	public void init(WebConnection connection) {
		if (ep == null) {
			throw new IllegalStateException(
					sm.getString("wsHttpUpgradeHandler.noPreInit"));
		}

		this.connection = connection;

		AbstractServletInputStream sis;
		AbstractServletOutputStream sos;
		try {
			sis = connection.getInputStream();
			sos = connection.getOutputStream();
		} catch (IOException e) {
			throw new IllegalStateException(e);
		}

		String httpSessionId = null;
		Object session = handshakeRequest.getHttpSession();
		if (session != null) {
			httpSessionId = ((HttpSession) session).getId();
		}

		// Need to call onOpen using the web application's class loader
		// Create the frame using the application's class loader so it can pick
		// up application specific config from the ServerContainerImpl
		Thread t = Thread.currentThread();
		ClassLoader cl = t.getContextClassLoader();
		t.setContextClassLoader(applicationClassLoader);
		try {
			WsRemoteEndpointImplServer wsRemoteEndpointServer =
					new WsRemoteEndpointImplServer(sos, webSocketContainer);
			wsSession = new WsSession(ep, wsRemoteEndpointServer,
					webSocketContainer, handshakeRequest.getRequestURI(),
					handshakeRequest.getParameterMap(),
					handshakeRequest.getQueryString(),
					handshakeRequest.getUserPrincipal(), httpSessionId,
					negotiatedExtensions, subProtocol, pathParameters, secure,
					endpointConfig);
			WsFrameServer wsFrame = new WsFrameServer(sis, wsSession, transformation);
			sos.setWriteListener(new WsWriteListener(this, wsRemoteEndpointServer));
			// WsFrame adds the necessary final transformations. Copy the
			// completed transformation chain to the remote end point.
			wsRemoteEndpointServer.setTransformation(wsFrame.getTransformation());
			ep.onOpen(wsSession, endpointConfig);
			webSocketContainer.registerSession(ep, wsSession);
			sis.setReadListener(new WsReadListener(this, wsFrame));
		} catch (DeploymentException e) {
			throw new IllegalArgumentException(e);
		} finally {
			t.setContextClassLoader(cl);
		}
	}

	@Override
	public void destroy() {
		if (connection != null) {
			try {
				connection.close();
			} catch (Exception e) {
				log.error(sm.getString("wsHttpUpgradeHandler.destroyFailed"), e);
			}
		}
	}

	private void onError(Throwable throwable) {
		wsSession.doClose(new CloseReason(CloseCodes.GOING_AWAY, throwable.getMessage()),
				new CloseReason(CloseCodes.CLOSED_ABNORMALLY, throwable.getMessage()));
		// Need to call onError using the web application's class loader
		Thread t = Thread.currentThread();
		ClassLoader cl = t.getContextClassLoader();
		t.setContextClassLoader(applicationClassLoader);
		try {
			ep.onError(wsSession, throwable);
		} finally {
			t.setContextClassLoader(cl);
		}
	}

	private void close(CloseReason cr) {
	    /*
         * Any call to this method is a result of a problem reading from the
         * client. At this point that state of the connection is unknown.
         * Attempt to send a close frame to the client and then close the socket
         * immediately. There is no point in waiting for a close frame from the
         * client because there is no guarantee that we can recover from
         * whatever messed up state the client put the connection into.
         */
		wsSession.onClose(cr);
	}

	private static class WsReadListener implements ReadListener {

		private final WsHttpUpgradeHandler wsProtocolHandler;
		private final WsFrameServer wsFrame;

		private WsReadListener(WsHttpUpgradeHandler wsProtocolHandler,
		                       WsFrameServer wsFrame) {
			this.wsProtocolHandler = wsProtocolHandler;
			this.wsFrame = wsFrame;
		}

		@Override
		public void onDataAvailable() {
			try {
				wsFrame.onDataAvailable();
			} catch (WsIOException ws) {
				wsProtocolHandler.close(ws.getCloseReason());
			} catch (IOException ioe) {
				onError(ioe);
				CloseReason cr = new CloseReason(
						CloseCodes.CLOSED_ABNORMALLY, ioe.getMessage());
				wsProtocolHandler.close(cr);
			}
		}

		@Override
		public void onAllDataRead() {
			// Will never happen with WebSocket
			throw new IllegalStateException();
		}

		@Override
		public void onError(Throwable throwable) {
			wsProtocolHandler.onError(throwable);
		}
	}

	private static class WsWriteListener implements WriteListener {

		private final WsHttpUpgradeHandler wsProtocolHandler;
		private final WsRemoteEndpointImplServer wsRemoteEndpointServer;

		private WsWriteListener(WsHttpUpgradeHandler wsProtocolHandler,
		                        WsRemoteEndpointImplServer wsRemoteEndpointServer) {
			this.wsProtocolHandler = wsProtocolHandler;
			this.wsRemoteEndpointServer = wsRemoteEndpointServer;
		}

		@Override
		public void onWritePossible() {
			// Triggered by the poller so this isn't the same thread that
			// triggered the write so no need for a dispatch
			wsRemoteEndpointServer.onWritePossible(false);
		}

		@Override
		public void onError(Throwable throwable) {
			wsProtocolHandler.onError(throwable);
			wsRemoteEndpointServer.close();
		}
	}
}
